Oxytocin and the social facilitation of placebo effects.

Significant clinical improvement is often observed in patients who receive placebo treatment in randomized double-blind placebo-controlled trials. While a proportion of this "improvement" reflects experimental design limitations (e.g., reliance on subjective outcomes, unbalanced groups, reporting biases), some of it reflects genuine improvement corroborated by physiological change. Converging evidence across diverse medical conditions suggests that clinically-relevant benefits from placebo treatment are associated with the activation of brain reward circuits. In parallel, evidence has accumulated showing that such benefits are facilitated by clinicians that demonstrate warmth and proficiency during interactions with patients. Here, we integrate research on these neural and social aspects of placebo effects with evidence linking oxytocin and social reward to advance a neurobiological account for the social facilitation of placebo effects. This account frames oxytocin as a key mediator of treatment success across a wide-spectrum of interventions that increase social connectedness, thereby providing a biological basis for assessing this fundamental non-specific element of medical care.

Rapid evolution of the primate larynx?

Tissue vibrations in the larynx produce most sounds that comprise vocal communication in mammals. Larynx morphology is thus predicted to be a key target for selection, particularly in species with highly developed vocal communication systems. Here, we present a novel database of digitally modeled scanned larynges from 55 different mammalian species, representing a wide range of body sizes in the primate and carnivoran orders. Using phylogenetic comparative methods, we demonstrate that the primate larynx has evolved more rapidly than the carnivoran larynx, resulting in a pattern of larger size and increased deviation from expected allometry with body size. These results imply fundamental differences between primates and carnivorans in the balance of selective forces that constrain larynx size and highlight an evolutionary flexibility in primates that may help explain why we have developed complex and diverse uses of the vocal organ for communication.

Selection on vocal output affects laryngeal morphology in rats.

Although laryngeal morphology often reflects adaptations for vocalization, the structural consequences of selection for particular aspects of vocal behavior remain poorly understood. In this study, we investigated the effects of increased ultrasonic calling in pups on the adult larynx morphology in selectively bred rat lines. Laryngeal morphology was assessed using multiple techniques: mineralized cartilage volumes were compared in 3D-models derived from microCT scans, internal structure was compared using clearing and staining procedures combined with microscopy, cellular structure was compared using histology and microscopy, and element composition was assessed with scanning energy dispersive X-ray spectroscopy. Our results show that adult rats from lines bred to produce ultrasonic calls at higher rates as pups have shorter vocal folds and a more mineralized thyroid cartilage compared to rats bred to produce ultrasonic calls at lower rates. The change in vocal fold length appears to account for differences in low-frequency calls in these two rat lines. We suggest that the observed increases in mineralization of the thyroid cartilage in the high-ultrasound lineage provide increased reinforcement of the laryngeal structure during ultrasonic call production. Our findings therefore demonstrate an effect of selection for vocal behavior on laryngeal morphology, with acoustic consequences.

Vocal similarity predicts the relative attraction of musical chords.

Musical chords are combinations of two or more tones played together. While many different chords are used in music, some are heard as more attractive (consonant) than others. We have previously suggested that, for reasons of biological advantage, human tonal preferences can be understood in terms of the spectral similarity of tone combinations to harmonic human vocalizations. Using the chromatic scale, we tested this theory further by assessing the perceived consonance of all possible dyads, triads, and tetrads within a single octave. Our results show that the consonance of chords is predicted by their relative similarity to voiced speech sounds. These observations support the hypothesis that the relative attraction of musical tone combinations is due, at least in part, to the biological advantages that accrue from recognizing and responding to conspecific vocal stimuli.

Progress without exclusion in the search for an evolutionary basis of music.

Mehr et al.'s hypothesis that the origins of music lie in credible signaling emerges here as a strong contender to explain early adaptive functions of music. Its integration with evolutionary biology and its specificity mark important contributions. However, much of the paper is dedicated to the exclusion of popular alternative hypotheses, which we argue is unjustified and premature.

Harmonicity and Roughness in the Biology of Tonal Aesthetics.

Evidence supporting a link between harmoni-city and the attractiveness of simultaneous tone combinations has emerged from an experiment designed to mitigate effects of musical enculturation. I examine the analysis undertaken to produce this evidence and clarify its relation to an account of tonal aesthetics based on the biology of auditory-vocal communication.

Is consonance attractive to budgerigars? No evidence from a place preference study.

Consonant tone combinations occur naturally in the overtone series of harmonic sounds. These include sounds that many non-human animals produce to communicate. As such, non-human animals may be attracted to consonant intervals, interpreting them, e.g., as a feature of important social stimuli. There is preliminary evidence of attraction to consonance in various bird species in the wild, but few experimental studies with birds. We tested budgerigars (Melopsittacus undulatus) for attraction to consonant over dissonant intervals in two experiments. In Experiment 1, we tested humans and budgerigars using a place preference paradigm in which individuals could explore an environment with multiple sound sources. Both species were tested with consonant and dissonant versions of a previously studied piano melody, and we recorded time spent with each stimulus as a measure of attraction. Human females spent more time with consonant than dissonant stimuli in this experiment, but human males spent equal time with both consonant and dissonant stimuli. Neither male nor female budgerigars spent more time with either stimulus type. In Experiment 2, we tested budgerigars with more ecologically relevant stimuli comprised of sampled budgerigar vocalizations arranged into consonant or dissonant chords. These stimuli, however, also failed to produce any evidence of preference in budgerigar responses. We discuss these results in the context of ongoing research on the study of consonance as a potential general feature of auditory perception in animals with harmonic vocalizations, with respect to similarities and differences between human and budgerigar vocal behaviour, and future methodological directions.

A biological rationale for musical consonance.

The basis of musical consonance has been debated for centuries without resolution. Three interpretations have been considered: (i) that consonance derives from the mathematical simplicity of small integer ratios; (ii) that consonance derives from the physical absence of interference between harmonic spectra; and (iii) that consonance derives from the advantages of recognizing biological vocalization and human vocalization in particular. Whereas the mathematical and physical explanations are at odds with the evidence that has now accumulated, biology provides a plausible explanation for this central issue in music and audition.

Humans recognize emotional arousal in vocalizations across all classes of terrestrial vertebrates: evidence for acoustic universals.

Writing over a century ago, Darwin hypothesized that vocal expression of emotion dates back to our earliest terrestrial ancestors. If this hypothesis is true, we should expect to find cross-species acoustic universals in emotional vocalizations. Studies suggest that acoustic attributes of aroused vocalizations are shared across many mammalian species, and that humans can use these attributes to infer emotional content. But do these acoustic attributes extend to non-mammalian vertebrates? In this study, we asked human participants to judge the emotional content of vocalizations of nine vertebrate species representing three different biological classes-Amphibia, Reptilia (non-aves and aves) and Mammalia. We found that humans are able to identify higher levels of arousal in vocalizations across all species. This result was consistent across different language groups (English, German and Mandarin native speakers), suggesting that this ability is biologically rooted in humans. Our findings indicate that humans use multiple acoustic parameters to infer relative arousal in vocalizations for each species, but mainly rely on fundamental frequency and spectral centre of gravity to identify higher arousal vocalizations across species. These results suggest that fundamental mechanisms of vocal emotional expression are shared among vertebrates and could represent a homologous signalling system.

More than words (and faces): evidence for a Stroop effect of prosody in emotion word processing.

Humans typically combine linguistic and nonlinguistic information to comprehend emotions. We adopted an emotion identification Stroop task to investigate how different channels interact in emotion communication. In experiment 1, synonyms of "happy" and "sad" were spoken with happy and sad prosody. Participants had more difficulty ignoring prosody than ignoring verbal content. In experiment 2, synonyms of "happy" and "sad" were spoken with happy and sad prosody, while happy or sad faces were displayed. Accuracy was lower when two channels expressed an emotion that was incongruent with the channel participants had to focus on, compared with the cross-channel congruence condition. When participants were required to focus on verbal content, accuracy was significantly lower also when prosody was incongruent with verbal content and face. This suggests that prosody biases emotional verbal content processing, even when conflicting with verbal content and face simultaneously. Implications for multimodal communication and language evolution studies are discussed.

Biological principles for music and mental health.

Efforts to integrate music into healthcare systems and wellness practices are accelerating but the biological foundations supporting these initiatives remain underappreciated. As a result, music-based interventions are often sidelined in medicine. Here, I bring together advances in music research from neuroscience, psychology, and psychiatry to bridge music's specific foundations in human biology with its specific therapeutic applications. The framework I propose organizes the neurophysiological effects of music around four core elements of human musicality: tonality, rhythm, reward, and sociality. For each, I review key concepts, biological bases, and evidence of clinical benefits. Within this framework, I outline a strategy to increase music's impact on health based on standardizing treatments and their alignment with individual differences in responsivity to these musical elements. I propose that an integrated biological understanding of human musicality-describing each element's functional origins, development, phylogeny, and neural bases-is critical to advancing rational applications of music in mental health and wellness.

ACOUSTICALLY-DRIVEN PHONEME REMOVAL THAT PRESERVES VOCAL AFFECT CUES.

In this paper, we propose a method for removing linguistic information from speech for the purpose of isolating paralinguistic indicators of affect. The immediate utility of this method lies in clinical tests of sensitivity to vocal affect that are not confounded by language, which is impaired in a variety of clinical populations. The method is based on simultaneous recordings of speech audio and electroglotto-graphic (EGG) signals. The speech audio signal is used to estimate the average vocal tract filter response and amplitude envelop. The EGG signal supplies a direct correlate of voice source activity that is mostly independent of phonetic articulation. These signals are used to create a third signal designed to capture as much paralinguistic information from the vocal production system as possible-maximizing the retention of bioacoustic cues to affect-while eliminating phonetic cues to verbal meaning. To evaluate the success of this method, we studied the perception of corresponding speech audio and transformed EGG signals in an affect rating experiment with online listeners. The results show a high degree of similarity in the perceived affect of matched signals, indicating that our method is effective.

Major and minor music compared to excited and subdued speech.

The affective impact of music arises from a variety of factors, including intensity, tempo, rhythm, and tonal relationships. The emotional coloring evoked by intensity, tempo, and rhythm appears to arise from association with the characteristics of human behavior in the corresponding condition; however, how and why particular tonal relationships in music convey distinct emotional effects are not clear. The hypothesis examined here is that major and minor tone collections elicit different affective reactions because their spectra are similar to the spectra of voiced speech uttered in different emotional states. To evaluate this possibility the spectra of the intervals that distinguish major and minor music were compared to the spectra of voiced segments in excited and subdued speech using fundamental frequency and frequency ratios as measures. Consistent with the hypothesis, the spectra of major intervals are more similar to spectra found in excited speech, whereas the spectra of particular minor intervals are more similar to the spectra of subdued speech. These results suggest that the characteristic affective impact of major and minor tone collections arises from associations routinely made between particular musical intervals and voiced speech.

Temporal modulation in speech, music, and animal vocal communication: evidence of conserved function.

Speech is a distinctive feature of our species. It is the default channel for language and constitutes our primary mode of social communication. Determining the evolutionary origins of speech is a challenging prospect, in large part because it appears to be unique in the animal kingdom. However, direct comparisons between speech and other forms of acoustic communication, both in humans (music) and animals (vocalization), suggest that important components of speech are shared across domains and species. In this review, we focus on a single aspect of speech-temporal patterning-examining similarities and differences across speech, music, and animal vocalization. Additional structure is provided by focusing on three specific functions of temporal patterning across domains: (1) emotional expression, (2) social interaction, and (3) unit identification. We hypothesize an evolutionary trajectory wherein the ability to identify units within a continuous stream of vocal sounds derives from social vocal interaction, which, in turn, derives from vocal emotional communication. This hypothesis implies that unit identification has parallels in music and precursors in animal vocal communication. Accordingly, we demonstrate the potential of comparisons between fundamental domains of biological acoustic communication to provide insight into the evolution of language.

Hear them roar: A comparison of black-capped chickadee (Poecile atricapillus) and human (Homo sapiens) perception of arousal in vocalizations across all classes of terrestrial vertebrates.

Recently, evidence for acoustic universals in vocal communication was found by demonstrating that humans can identify levels of arousal in vocalizations produced by species across three biological classes (Filippi et al., 2017). Here, we extend this work by testing whether two vocal learning species, humans and chickadees, can discriminate vocalizations of high and low arousal using operant discrimination go/no-go tasks. Stimuli included vocalizations from nine species: giant panda, American alligator, common raven, hourglass treefrog, African elephant, Barbary macaque, domestic pig, black-capped chickadee, and human. Subjects were trained to respond to high or low arousal vocalizations, then tested with additional high and low arousal vocalizations produced by each species. Chickadees (Experiment 1) and humans (Experiment 2) learned to discriminate between high and low arousal stimuli and significantly transferred the discrimination to additional panda, human, and chickadee vocalizations. Finally, we conducted discriminant function analyses using four acoustic measures, finding evidence suggesting that fundamental frequency played a role in responding during the task. However, these analyses also suggest roles for other acoustic factors as well as familiarity. In sum, the results from these studies provide evidence that chickadees and humans are capable of perceiving arousal in vocalizations produced by multiple species. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Pupillometry of Groove: Evidence for Noradrenergic Arousal in the Link Between Music and Movement.

The capacity to entrain motor action to rhythmic auditory stimulation is highly developed in humans and extremely limited in our closest relatives. An important aspect of auditory-motor entrainment is that not all forms of rhythmic stimulation motivate movement to the same degree. This variation is captured by the concept of musical groove: high-groove music stimulates a strong desire for movement, whereas low-groove music does not. Here, we utilize this difference to investigate the neurophysiological basis of our capacity for auditory-motor entrainment. In a series of three experiments we examine pupillary responses to musical stimuli varying in groove. Our results show stronger pupil dilation in response to (1) high- vs. low-groove music, (2) high vs. low spectral content, and (3) syncopated vs. straight drum patterns. We additionally report evidence for consistent sex differences in music-induced pupillary responses, with males exhibiting larger differences between responses, but females exhibiting stronger responses overall. These results imply that the biological link between movement and auditory rhythms in our species is supported by the capacity of high-groove music to stimulate arousal in the central and peripheral nervous system, presumably via highly conserved noradrenergic mechanisms.

Publisher Correction: Acoustic allometry revisited: morphological determinants of fundamental frequency in primate vocal production.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.